Stent Removal Snare and Dilator

ABSTRACT

A tool for removing non-visually, urinary tract stents placed within the urinary tract of a patient, comprising a distal end, a longitudinally-extending stem, and a handle. The distal end has a conical head with a groove for hooking a stent, stent string or similar stent configuration. The snare head may have a channel for advancing the tool through a urethra over a guide wire. The snare head has a narrow conical front end for dilating urethral strictures. The stem connects the snare head to the snare handle and is made to be flexible or bend on encountering resistance.

FIELD OF INVENTION

The present invention is in the field of stent removal. Moreparticularly, the present invention is in the field of the nonvisualremoval of ureteral stents.

BACKGROUND OF INVENTION

The urinary tract is susceptible to the obstruction of urine flow eitherby endogenous causes such as the formation of stones, externalcompression by anatomic abnormalities, or neoplastic growth. Obstructioncan also be iatrogenic, induced by manipulation or surgery. Ureteralstents have been developed to bypass such urinary tract obstructions.Typically, ureteral stents are made of biocompatible plastic materials.During a typical surgical procedure to bypass a urinary tractobstruction, the ureteral stent is passed over a guide wire. The stentis tubular to allow for the flow of urine, just large enough to fit overa guide wire, but of several diameters within a small range (2-3 mm) andwith “S” shaped ends which act as anchors that prevent the stent'smigration. The ureteral stents are often placed at the end of anoperation or by themselves, when no other procedure is indicated, butthe relief of the obstruction.

Typically, ureteral stents are introduced through the urethra via afiberoptic endoscopic instrument, such as for example, a cystoscope. Theset-up for an endoscopic procedure typically includes light and watersources, and local anesthesia or sedation. Stent removal is alsotypically performed using fiberoptic endoscopic instruments. Fiberopticendoscopic instruments are generally guided through a urethra visually,with a doctor manually guiding the endoscope based on the imagesobserved through the fiberscope. The endoscopic instrument is typicallyguided to the stent at which point it is removed with a “foreign body”grasper.

Visually guiding endoscopes through the urinary tract in this manner isoften labor intensive, and requires special set-up and assistant time.Moreover, some endoscopes are large enough to allow for the passageforeign body graspers, causing discomfort for patients. Fluid flow andlocal anesthetics are also frequently used during removal procedures,however discomfort is not completely eliminated. Attempts have been madeto remove stents without relying on visual instruments such as acystoscope by attaching a string to the stent. However, the strings tendto retract and reside within the urethra still requiring the use of acystoscope for their retrieval.

Other drawbacks exist.

SUMMARY OF THE INVENTION

Embodiments of a tool and method for removing urinary tract stentswithout a visual aid are disclosed. In one embodiment of the stentsnare, the stent snare for removing stents includes a conical head forhooking a ureteral stent, a handle for controlling the passage of theconical head through the urethra and a stem extending from the head tothe handle. In embodiments of the invention, the conical head has afront end for dilating a urethra as the stent snare passes through theurethra, and a base end having a snare. Embodiments of the invention mayalso include a channel for guiding the snare head over a guide wire. Thetool's ability to slide over a guide wire gives it better accuracy totravel through distorted, narrowed, scarred portions of the urethra, andprevents the formation of false passages, which can occur with blinddilation. Embodiments of the invention allow for easier removal ofindwelling ureteral stents without the need for visual aids, and for thedilation of urethral strictures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram of a side view of a stent snare head according toone embodiment of the invention.

FIG. 1B is a diagram of a front view of a stent snare head according toone embodiment of the invention.

FIG. 2A is a diagram of a side view of a stent snare stem according toone embodiment of the invention.

FIG. 2B is a diagram of a side and front view of a stent snare handleaccording to one embodiment of the invention.

FIG. 3 is an illustration of a stent snare removal tool removing a stentfrom a urethra according to one embodiment of the invention.

FIG. 4 is an illustration of a stent snare removal tool removing a stentfrom a urethra according to another embodiment of the invention.

FIG. 5 is an illustration of a plane view of the stent snare removaltool according to one embodiment of the invention.

FIG. 6 is an illustration of a plane view of the stent from the handleend.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1A and 1B, a stent snare head according to oneembodiment of the invention is depicted. A stent snare head may have aconical shape, with a front end 105, base end 114, bottom exteriorsurface 106, and top exterior surface 104. The front dilating end 105may be conical or leveled as depicted in FIG. 1A. The base end 114 mayhave a snare formed by a snare hook having interior surface 102 andexterior surface 103 and snare base having interior surface 101 andexterior surface 107. The snare hook and snare base may form a grooveacross a portion of the base end, having length 108. The bottom exteriorsurface 106 may be straight, diagonal, or arcuated as depicted in theFIGS. 1A and 1B. According to some embodiments, the snare head may havea channel 115 running from the front dilating end 105 through to thebase end 114.

According to some embodiments of the invention, the top exterior surface104 of the exterior of the head extends beyond the base, forming theexterior surface of the snare hook 103. The bottom surface 106 may alsoextend beyond the base, forming the exterior of the snare base 107. FIG.1A depicts a side view of the first surface 102. FIG. 1B illustrates across-sectional view of the snare hook and snare base according to oneembodiment of the invention. The snare hook and snare base may be flator rounded as FIG. 1B illustrates. For example, as FIG. 1B illustrates,the snare hook and snare base are rounded in the same annular shape asthe snare head.

In another aspect of the invention, the snare may include a longitudinalchannel 105. The longitudinal channel 115 may extend from the tip of thesnare head 105 through the base of the snare head 114. The longitudinalchannel 105 guides the snare head over a guide wire (not pictured),through a urethra.

The groove formed by the snare hook and base are used to hook the “S”configuration of a bladder curl residing inside the bladder, or of astent string lodged in the urethra. The bladder curl of a stent isgenerally characterized as a flexible curl in the shape of an “S” at oneend of the stent. Generally, the bladder curls keep the stent positionedbetween the kidney and the bladder and prevents migration. According toone embodiment, the snare hook may remove the stent by attaching to thebladder curl. Specifically, the stent may be removed by inserting thesnare into the bladder, hooking the curl of the stent lodged in thebladder, and pulling the snare from the bladder with a sliding motion.

According to further embodiments, the snare hook may also be used toremove stents of other shapes and configurations. For example, the stentsnare may also be used to trap the string portion of a stent usuallyfound in the urethra. Stent strings may have a tail made of nylonthread, which can hang into the urethra, and have a loop configurationat the end. In some embodiments, the strings may also have a lassoconfiguration. In further embodiments, the loop or lasso may be createdat the time of insertion. The snare hook may attach to the string andremove the snare by pulling on the string, as described above. However,when removing a stent by its nylon thread, the snare does not have toadvance into the bladder as when being removed by the bladder curl.

According to other embodiments, the snare may be advanced into a bladderover a guide wire. A guide wire may be first passed through the meatusof the urethra manually. The guide wire may then be threaded through thechannel 115 of the snare head. The snare may then be advanced into thebladder over a guide wire passing through channel 115. As the snare headadvances over the guide wire, the dilating front end dilates anddisrupts scar tissue inside the urethra, if present. Once the snare isin the bladder, the stent may be trapped manually and removed accordingto the pulling motions described above. The guide wire thereby allowsthe tool to be accurately advanced through distorted, narrowed, scarredportions of a urethra, and also prevents the formation of falsepassages, which can occur with blind dilation.

According to some embodiments of the invention, the snare base mayfurther include a hole 116 for affixing a stem and handle. FIG. 1Billustrates the cross sectional view of the hole 112. Affixing the stemand handle to the snare head with hole 116, 112 provides greater controlover the snare head and improved durability of the snare and stem.

In one aspect of the invention, the dilating front end 105 of the snarehas a height between the bottom surface 106 and top surface 103 thatgradually increases from the front of the head 105 to the base 114, todilate the urethra as the snare is inserted through a urethra stricture.For example, in one embodiment, the head has a diameter between 2.5 mmand 6 mm at its widest circumference. Snare heads of this size allowsfor dilation of between 8 F and 18 F. Other sizes can increase thedilation to 22 F, 24 F or 28 F.

FIG. 2A depicts a stem 228 according to one embodiment of the invention.The stem 228 longitudinally extends from the snare head to the handle221. The stem is attached to the snare head by hole 116 (also depictedas 227). The stem is inserted off center on the head as not to interferewith the channel 115. In one aspect of the invention, the stem has aspringing action that allows the snare head to slide through the distalurethra and the proximal tortuous urethra, without undue trauma. Thespring quality provides tactile feedback to the operator in case ofmeeting resistance. The spring quality comes from the quality of thematerial, which is drawn thin enough to be flexible and “give” uponmeeting resistance.

In one aspect of the invention, the stem may also have markings toindicate the distance from the handle, which in turn, indicates thedistance the snare head has been inserted into the urethra. The markingsmay include an indication of the diameter of the tool. FIG. 2Billustrates a handle attachment according to one embodiment of theinvention. The handle attachment 221 controls the stem 228 and snarehead as they advance through the urethra. The handle has a hole 214, 222for attaching to a stem, and aligning the handle in the transverse planeof the head. The handle may have a width 216, and height 219. As thecross-section illustration of the handle shows, the handle 221 may betrapezoidal, allowing for convenient and ergonomic manipulation of thetool. However, in other embodiments, the handle may be square, round, ortriangular. In one aspect of the invention, the handle may include anidentification of the manufacturer on the flat surface of the handle.

FIG. 3 depicts a method of removing a stent from a female urethra with astent snare removal tool removing according to one embodiment of theinvention. FIG. 3 shows a female urethra 303 having a bladder wall 301,right ureter 302 and stent 304. The stent has a bladder curl 305. Thehandle 307 is used to advance the snare head 306 through the urethra.The groove of the snare head may hook onto a bladder curl 305. Once thesnare groove has attached to the snare head, the stent may be removed bygently pulling on the stent curl with the snare head.

FIG. 4 depicts a method of removing a stent from a male urethra with astent snare removal tool according to another embodiment of theinvention. A stent 401 has a stent bladder curl 402 has a stent string403, which has been configured with a lasso or loop 404. The groove ofthe snare head 405 hooks onto the lasso or loop of the stent stringoutside the bladder, before the stent head 405 advances through theprostate 408. The snare head 405 may be advanced through the urethra bymanipulating the handle 407 and stem 406.

FIG. 5 illustrates a plane view of the snare head according to oneembodiment of the invention. The snare head has a front dilating end501, groove 502, exterior surface 503, snare hook 504, channel 505 andstem 506.

In a preferred embodiment, the snare head has 10 mm in length and has aradius of 6 mm at the widest dimension. The channel 115 has a radius of0.5 mm to allow travel over a guide wire, and a groove 3 mm wide.

According to some embodiments, the snare head may be constructed out ofsurgical steel, plastic or hard polymers. The snare head may be finishedwith a smooth surface, to allow for non-traumatic travel through theurethra. In a different embodiment the snare head may have the shape ofa coil with the “hook” element being the space between the coils. Inanother embodiment the groove may be placed horizontal (or 90 degrees)to the longitudinal axis of the tool. In a preferred embodiment, thesnare head, stem and handle are made from a biologically inert material,such as surgical-quality stainless steel. In other embodiments, the headis made from metal and the remainder of the body is made from a plasticmaterial.

What is claimed is:
 1. A stent snare for removing urinary tract stents,the stent snare comprising: a. a conical head for hooking a ureteralstent, the conical head comprising i. a dilating front end for dilatinga urethra as the stent snare passes through the urethra, ii. a base endopposite the front end, the base end comprising a snare formed by the“U” shaped circumference of the base end; iii. this “U” shaped groovecan be placed at different angles to the longitudinal axis of the tool.iv. The conical shaped head can be of one solid piece or made to looklike a coil. b. a handle for controlling the passage of the conical headthrough the urethra; and c. a stem longitudinally extending from thehead to the handle.
 2. The stent snare of claim 1, wherein the conicalhead further comprises a channel extending longitudinally from the frontend through the base end for guiding the stent snare over a guide wire.3. The stent snare of claim 1, wherein the stem further comprises aflexible spring.
 4. The stent snare of claim 1, wherein the conicalhead, the handle, and the stem are made of a biologically inert materialselected from a group consisting steel, plastic, and hard polymer. 5.The stent snare of claim 1, wherein the stem is 25.5 cm in length. 6.The stent snare of claim 2, wherein the conical head is 10 mm in length,the front end has a diameter of 2.5 mm, the base end has a diameter of 6mm, and the channel has a radius of 0.5 mm.
 7. The stent snare of claim1, wherein the conical head has a smooth surface to allow fornon-traumatic travel through the urethra.
 8. The stent snare of claim 1,wherein the stem provides markings indicating the distance the snare hastraveled in the urethra
 9. A method for removing a ureteral stent with astent snare without visual aid, the stent snare comprising a conicalhead for hooking a ureteral stent, the conical head comprising adilating front end for dilating the urethra as the stent snare passesthrough the urethra, a base end opposite the front end, the base endcomprising a snare formed on the circumference of the base end, and achannel extending longitudinally from the front end for guiding thestent over a guide wire, a handle for controlling the passage of theconical head through the urethra, and a stem longitudinally extendingfrom the head to the handle, the method comprising the steps of: a.passing the stent snare into the urethra; and b. snaring the string tailof a ureteral stent resting in the urethra or the base of the bladder.10. The method of claim 9, wherein the step of passing the stent intothe bladder comprises mapping the location of the stent with ultrasoundand hooking the stent with the snare under ultrasound guidance.
 11. Themethod of claim 9, wherein the stent snare is passed into the urethraover a guide wire.
 12. The method of claim 9, wherein the stent snare ispassed into the urethra without a guide wire.
 13. The method of claim 9,wherein the stent snare is passed into a urinary bladder over a guidewire.
 14. The method of claim 9, wherein the step of passing the stentsnare comprises the step of dilating the urethral stricture by guidanceover a guide wire.